问题 选择题

速度的大小和方向都不断变化,但加速度的大小和方向都不变的运动是(  )

A.匀速圆周运动

B.平抛物体的运动

C.自由落体运动

D.竖直上抛运动

答案

A、匀速圆周运动的速度大小不变,方向改变,加速度的大小不变,方向时刻改变,始终指向圆心.故A错误.

B、平抛运动的速度大小和方向都在改变,加速度大小和方向都不变.故B正确.

C、自由落体运动的速度方向不变,大小在变化.加速度大小方向都不变.故C错误.

D、竖直上抛运动的过程中,速度大小在变化,方向不是不断变化,但是加速度大小方向不变.故D错误.

故选B.

阅读理解

仔细阅读,选择正确答案。

Dear Sir,

I have to travel every day from Souk Road to the airport. Two buses travel along the line: the number 49 and number 16. But by the time the number 16 bus gets to Souk Road, it is always full, so I can’t get on it. I have to wait for the number 49, because sometimes there are empty seats on it.

The timetable says that there are buses from Souk Road to the airport every ten minutes. If this is so, why do I have to wait half an hour for a bus every day?

The regulations(规章)say that if there are empty seats on a bus, the bus must stop at every stop where people are waiting. Why do the half-empty buses go straight past me when I am standing at the bus stop?

The regulations say that no bus may carry more than 40 seated passengers(乘客)and 20 standing passengers. Yesterday I was the first to get off the bus when it reached the airport. I counted(数)the other passengers as they got off. There were 129 of them.

It is clear that our bus companies break the regulations and think little of their passengers. Can nothing be done to make your service(服务)better?

A. a message        B. a talk       C. a story      D. a letter

小题1:The writer has to take Bus No. 49 because _________.

A.it arrives on time

B.it is not always full

C.it travels faster

D.it has fewer seats on it小题2:How long does the writer usually have to wait for a bus?

A.Ten minutes.

B.One hour.

C.Half an hour.

D.Nearly a day.小题3:The regulations say that each bus may carry ______ passengers at most.

A. 20           B. 40       C. 60       129

小题4:From the passage we can see that __________.

A.the bus service was bad

B.no passengers took their buses

C.no bus passed Souk Road

D.the writer was always the first to get on the bus

单项选择题